ATL: TWELVE - Advisories

[cycloneye]

BULLETIN
Tropical Depression Twelve Advisory Number 1
NWS National Hurricane Center Miami FL AL122022
500 PM AST Tue Oct 04 2022

...TROPICAL DEPRESSION FORMS WEST OF THE CABO VERDE ISLANDS...
...EXPECTED TO BE SHORT LIVED...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...14.9N 30.5W
ABOUT 440 MI...705 KM W OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES



Tropical Depression Twelve Discussion Number 1
NWS National Hurricane Center Miami FL AL122022
500 PM AST Tue Oct 04 2022

A fairly concentrated area of deep convection has persisted near an
area of low pressure that NHC has monitoring a few hundred miles
west of the Cabo Verde Islands, and Dvorak classifications from TAFB
and SAB are now a consensus T2.0/30 kt. It hadn't been clear
previously how well-defined the system was, but an ASCAT-C
scatterometer pass from this morning suggested that a small
circulation, with a well-defined center, had formed within the
broader trough located over the eastern Atlantic. Therefore,
advisories are being initiated on Tropical Depression Twelve with
maximum sustained winds of 30 kt.

The depression is located along the southwestern periphery of a
mid-level high centered over northwestern Africa, and to the south
of a prominent mid- to upper-level low. This pattern should steer
the cyclone northwestward or north-northwestward during the next
couple of days. The HWRF model is somewhat of an outlier to the
northeast and is therefore pulling the track model consensus aids in
that direction. The NHC track is near or to the west of the
consensus aids, more closely following the GFS and ECWMF global
models.

Deep-layer southwesterly shear is already beginning to increase over
the depression, and is likely to reach values of 30 to 35 kt in the
next 36 to 48 hours. The system has some potential to strengthen
slightly and reach tropical storm strength tonight or on Wednesday,
but for the most part the cyclone is expected to be short-lived.
Global models show the system opening up into a trough in a few
days, and the NHC forecast shows dissipation by 60 hours, which
could be a little generous.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 14.9N 30.5W 30 KT 35 MPH
12H 05/0600Z 15.9N 31.3W 35 KT 40 MPH
24H 05/1800Z 17.4N 32.2W 35 KT 40 MPH
36H 06/0600Z 18.9N 33.6W 35 KT 40 MPH
48H 06/1800Z 20.5N 35.3W 30 KT 35 MPH
60H 07/0600Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

BULLETIN
Tropical Depression Twelve Advisory Number 2
NWS National Hurricane Center Miami FL AL122022
1100 PM AST Tue Oct 04 2022

...DEPRESSION FORECAST TO DISSIPATE IN A COUPLE OF DAYS...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...15.3N 30.4W
ABOUT 430 MI...690 KM W OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNW OR 335 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES



Tropical Depression Twelve Discussion Number 2
NWS National Hurricane Center Miami FL AL122022
1100 PM AST Tue Oct 04 2022

The convective structure associated with the depression this evening
appears to be evolving from one that previously had the center
embedded in deep convection to more of a shear pattern, with only a
singular burst of deep convection occuring to the east of the
estimated center. This evolution is a result of southwesterly
vertical wind shear which is increasing over the system currently.
Unfortunately scatterometer data this evening largely missed the
small circulation. Subjective and objective Dvorak estimates remain
unchanged from 6 hours ago, and thus the latest intensity is held at
30 kt for this advisory.

The depression remains positioned along the southwestern side of a
mid-level ridge which is helping to steer the system generally
north-northwestward, estimated at 335/8-kt. This synoptic steering
pattern should remain in place with a strong mid- to upper-level low
maintaining the weakness north of the cyclone. The latest track
forecast was only nudged just a bit westward, shifting the NHC track
in the direction of the consensus aids.

The previously mentioned shear is expected to increase further to
over 30 kt in about 24 hours, with sea surface temperatures
gradually decreasing along the forecast track. The global and
regional hurricane model guidance responds to this unfavorable
environment by opening up the circulation of the depression into a
surface trough sometime in the 36-48 hour period. The latest
forecast now shows little intensification with the depression
dissipating in 48 hours.

It should be noted that some of the deterministic and ensemble model
guidance suggest that the forecast remains of this system may have
an opportunity to regenerate back into a tropical cyclone in the
subtropical Atlantic well away from land in about 5 days. At this
juncture, that possibility will not be reflected in the current
forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 15.3N 30.4W 30 KT 35 MPH
12H 05/1200Z 16.3N 31.5W 30 KT 35 MPH
24H 06/0000Z 17.7N 32.7W 30 KT 35 MPH
36H 06/1200Z 19.1N 34.2W 30 KT 35 MPH
48H 07/0000Z...DISSIPATED

$$
Forecaster Papin

[cycloneye]

Tropical Depression Twelve Discussion Number 3
NWS National Hurricane Center Miami FL AL122022
500 AM AST Wed Oct 05 2022

The depression is a sheared tropical cyclone, with the low-level
center displaced about 40 n mi to the west-southwest of the main
area of deep convection. Overall, the system is quite
ragged-looking and elongated from south to north, with little
evidence of banding. The current intensity estimate is held at 30
kt in agreement with Dvorak estimates from TAFB and SAB, although
this may be generous.

Southwesterly flow associated with a large upper-level low
centered about 700 n mi to the north of the depression is imparting
strong shear on the system. Global model guidance indicates that
this shear will continue, and increase, over the next 48 hours or
so while the tropical cyclone moves over waters of diminishing
oceanic heat content. These negative environmental factors should
result in the system dissipating in a couple of days. This is in
general agreement with the latest LGEM intensity guidance, and with
the global model guidance that shows the system opening up into a
trough by late Thursday.

The depression is moving somewhat to the left of previous estimates
with an initial motion of 320/7 kt. Over the next day or two, the
system is expected to move along the southwestern side of a
mid-level ridge over the eastern Atlantic. The official track
forecast is a little to the left of the previous one, but to the
right of the model consensus. This is close to the latest ECMWF
track prediction.

As noted earlier, some of the model guidance, notably the ECMWF,
and its ensemble, hints that the system could make a comeback after
5 days over the subtropical Atlantic. Given the uncertainties,
this will not be shown in the official forecast at this time.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0900Z 15.8N 31.2W 30 KT 35 MPH
12H 05/1800Z 16.8N 32.1W 30 KT 35 MPH
24H 06/0600Z 17.9N 33.7W 30 KT 35 MPH
36H 06/1800Z 19.1N 35.3W 25 KT 30 MPH
48H 07/0600Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Tropical Depression Twelve Discussion Number 4
NWS National Hurricane Center Miami FL AL122022
1100 AM AST Wed Oct 05 2022

The depression continues to lose organization. Visible satellite
imagery reveals an exposed low-level swirl displaced nearly 90 n mi
west of its associated deep convection due to strong
west-southwesterly vertical wind shear. The initial advisory
intensity of 30 kt may be a little generous, and is based off a
blend of the latest Dvorak intensity estimates. The shear affecting
the depression is forecast to increase further, while the system
ingests dry air to its west. This should disrupt significant deep
convection from reforming near its low-level center. In fact,
simulated satellite imagery from the GFS and ECMWF suggest that the
deep convection will not return and the system should become a
remnant low within the next 24 h. The latest NHC intensity forecast
is unchanged from the previous one. However, the forecast now
indicates that the depression will become a remnant low by 24 h.

The 12 h motion of the depression is about 295/8 kt. However, the
low-level center has been moving nearly westward over the past
several hours. Most of the model guidance indicates a
west-northwestward track to the south-southwest of a mid-level ridge
over the next couple days until dissipation. The NHC track forecast
has been adjusted to the left of the previous one and is on the
left side of the guidance envelope, as it is assumed that the
shallow low-level circulation is going to be steered more by the
low-level flow than the models indicate.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 15.6N 32.0W 30 KT 35 MPH
12H 06/0000Z 16.1N 33.2W 30 KT 35 MPH
24H 06/1200Z 17.0N 35.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/0000Z 18.1N 37.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 07/1200Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

BULLETIN
Tropical Depression Twelve Advisory Number 5
NWS National Hurricane Center Miami FL AL122022
500 PM AST Wed Oct 05 2022

...DEPRESSION EXPECTED TO BECOME A REMNANT LOW THURSDAY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...16.3N 32.4W
ABOUT 555 MI...895 KM W OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


Tropical Depression Twelve Discussion Number 5
NWS National Hurricane Center Miami FL AL122022
500 PM AST Wed Oct 05 2022

Deep convection had been stripped away well to the northeast of the
depression's low-level center for much of the morning. Just
recently, there has been a small burst of convection occurring
nearer to the center. The Dvorak intensity estimates have changed
little from the previous advisory. Therefore, the initial advisory
remains 30 kt. Persistent, strong southwesterly shear and dry air
entrainment should cause the depression to struggle to maintain
organized deep convection, and the system is forecast to become a
remnant low on Thursday. Based on some of the global model pressure
fields, it is possible that the surface low may become ill-defined
by Thursday as well, if not shortly thereafter. There was no change
to the NHC intensity forecast from the previous one.

After wobbling westward for a few hours this morning, the depression
has resumed a west-northwestward motion, or 300/9 kt. This general
motion is expected to continue until the system dissipates in a
couple of days as it remains to the south-southwest of a subtropical
ridge. The latest NHC track forecast was little changed from the
previous one.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 16.3N 32.4W 30 KT 35 MPH
12H 06/0600Z 17.1N 33.5W 30 KT 35 MPH
24H 06/1800Z 18.2N 35.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 07/0600Z 19.0N 37.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 07/1800Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

BULLETIN
Tropical Depression Twelve Advisory Number 6
NWS National Hurricane Center Miami FL AL122022
1100 PM AST Wed Oct 05 2022

...DEPRESSION HANGING ON TO TROPICAL CYCLONE STATUS FOR NOW...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.7N 32.5W
ABOUT 575 MI...925 KM WNW OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES



Tropical Depression Twelve Discussion Number 6
NWS National Hurricane Center Miami FL AL122022
1100 PM AST Wed Oct 05 2022

Occasional pulses of deep convection with cloud top temperatures
below -70 C continue to occur near and to the northeast of the
center of the tropical depression. We finally were able to receive
some scatterometer data near the system, with the highest
non-flagged wind retrievals of 28 and 32 kts from both ASCAT-B/C
passes. Subjective and objective Dvorak T-numbers have been
decreasing, but in deference to the higher scatterometer data, the
initial intensity was held at 30 kt for this advisory. The
southwesterly vertical wind shear over the depression is now above
30 kts, and is expected to increase further over the next 24 hours.
This highly unfavorable environment should ultimately lead to the
system's demise as the remaining deep convection is stripped
completely away from the low-level circulation. The intensity
forecast still shows the depression becoming a remnant low in 24
hours and then opening up into a trough in 48 hours, though this
could occur as soon as tomorrow morning.

The depression has made a northward jog this evening, but smoothing
out the 12 hour motion results in a northwest heading at 320/11 kt.
A northwest to west-northwest motion is expected to continue until
the system becomes a remnant low or dissipates in 24-48 hours. The
NHC track has been adjusted a bit northward due to the initial
position, but ends up near the previous forecast track in about 48
hours, following along with the consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 17.7N 32.5W 30 KT 35 MPH
12H 06/1200Z 18.7N 33.6W 30 KT 35 MPH
24H 07/0000Z 19.4N 35.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/1200Z 20.3N 38.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 08/0000Z...DISSIPATED

$$
Forecaster Papin

[cycloneye]

Tropical Depression Twelve Discussion Number 7
NWS National Hurricane Center Miami FL AL122022
500 AM AST Thu Oct 06 2022

Once again, the low-level circulation of the depression has
separated from the deep convection, which is located over 50 miles
to the east-northeast of the center. Subjective satellite intensity
estimates have held steady and the initial intensity remains at 30
kt. The already strong west-southwesterly vertical wind shear is
forecast to increase further in the next day or so and will likely
cause the cyclone to weaken quickly. Most of the global models
suggest the system will open into a trough within a day or two. The
official forecast now shows the depression becoming a post-tropical
remnant low in 12 hours and dissipated by 36 hours.

The depression is moving west-northwestward at about 11 kt. This
general motion is expected to continue for the next day or so while
the system follows the low-level flow around a ridge to the north.
The NHC track forecast has shifted south from the previous forecast
possibly due to the more westward initial position and is on the
northern edge of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 18.0N 33.4W 30 KT 35 MPH
12H 06/1800Z 18.8N 34.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 07/0600Z 19.3N 37.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 07/1800Z...DISSIPATED

$$
Forecaster Bucci

[cycloneye]

Tropical Depression Twelve Discussion Number 8
NWS National Hurricane Center Miami FL AL122022
1100 AM AST Thu Oct 06 2022

Deep convection redeveloped near the low-level center early this
morning. However, since that time the convection has become sheared
off to the east-northeast of the center and is dissipating. A recent
partial scatterometer overpass showed some 25-30 kt wind vectors
near the decaying convection. Therefore, the initial advisory
intensity is set at 30 kt. Strong west-southwesterly shear is
expected to increase further while the surrounding thermodynamic
environment continues to dry out over the next couple of days.
Therefore, it is still anticipated that the depression will
degenerate into a remnant low soon, and dissipate in a day or so.
The NHC intensity forecast is unchanged from the previous one.

The depression is moving west-northwestward at about 10 kt. A turn
to the west is expected by tonight while the system moves in the
low-level flow around a ridge to the north. The NHC track forecast
is little changed from the previous one and is near the multi-model
consensus tracks.


FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 18.3N 34.4W 30 KT 35 MPH
12H 07/0000Z 18.8N 36.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 07/1200Z 18.8N 38.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 08/0000Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Tropical Depression Twelve Discussion Number 9
NWS National Hurricane Center Miami FL AL122022
500 PM AST Thu Oct 06 2022

By definition, the depression may no longer be considered a tropical
cyclone. The current convection can not really be considered
organized, and consists of a couple of updrafts with an enhanced
cirrus canopy due to about 40 kt of west-southwesterly shear. This
lack of organized deep convection with the depression has persisted
since around 10 UTC this morning. An earlier scatterometer overpass
showed winds no higher than 25 kt near the circulation. Between
this data and the latest Dvorak intensity estimates, the initial
advisory intensity has been lowered to 25 kt. The very strong shear
is expected to continue to impact the depression for the foreseeable
future while the environmental relative humidity continues to
decrease. Therefore, the system should be able to be declared a
remnant low tonight, if there is no evidence that the system has
opened up into a trough before that time. The NHC intensity
forecast was lowered due to the weaker initial intensity.

The depression is moving west-northwestward at about 13 kt. A turn
to the west is expected by tonight while the system moves in the
low-level flow to the south a subtropical ridge. The NHC track
forecast is essentially unchanged from the previous one and is near
the multi-model consensus tracks.


FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 18.8N 35.8W 25 KT 30 MPH
12H 07/0600Z 19.0N 37.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 07/1800Z 19.0N 41.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 08/0600Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Remnants Of Twelve Discussion Number 10
NWS National Hurricane Center Miami FL AL122022
1100 PM AST Thu Oct 06 2022

Since the previous advisory, the center of the depression, or what
remains of it, has become further separated by a small, highly
sheared area of colder cloud tops. In addition, the center has
become less defined, and low-level GOES-16 derived motion winds no
longer indicate the system has a closed circulation. This structure
was confirmed by a recent ASCAT-B pass, which showed the system has
degenerated into a surface trough, albeit one that still has winds
up to 30 kt to its northeast. Thus, this will be the last advisory
on the system.

The motion of the remnant low-level cloud swirl is moving just north
of due west at 290/15 kt. This motion should continue until the
vorticity maxima completely dissipates.

Additional information on this system can be found in High Seas
Forecasts issued by the National Weather Service, under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php


FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 18.6N 36.8W 30 KT 35 MPH...REMNANTS
12H 07/1200Z...DISSIPATED

$$
Forecaster Papin